(est-format-unit): Treat `image-list' as the same as `list'.
(est-format-unit): Support `img' tag.
(est-format-props): Don't apply `www-format-encode-string' to the return value of `est-format-unit' because it has already been encoded.
(est-format-unit): For conversion of `feature-name' unit, enclose '(a (:href ...) ...) with (span (:class "feature-name") ...)
(est-format-unit): Support `est-hide-cgi-mode'.
(est-format-unit): Format `omitted'.
(est-format-list): Don't specify separator for each child unit.
(est-format-unit): Support :subtype property of list node; if subtype `unordered-list' is specified, use <ul> tag. (est-format-list): Likewise.
(est-format-unit): Change optional argument `without-tags' to `output-format'; now `output-format' accepts various formats such as 'html, 'plain-text and 'wiki-text instead of nil and non-nil. (est-format-list): Likewise.
(est-format-unit): Accept <img>.
(est-format-unit): Fix bug about `feature-name'; modify for `www-uri-make-feature-name-url'.
New files.